A transfer feeder equipped for a conventional transfer press is provided with a pair of transfer bars in a feeding direction, and a work is carried in and out to and from a press by the transfer bars, through the operation thereof in a two-dimensional or three-dimensional direction in synchronism of the transfer bars with the press, to thereby carry out the conveyance between respective working stations.
The transfer feeder is also provided with a driving mechanism for driving the transfer bars in the two or three dimensional direction, and a camshaft driven by power taken out of the press is provided for the driving mechanism. To the camshaft are mounted a feed cam and a lift cam by which a feed lever and a lift lever are swung through cam followers, respectively, whereby the transfer bars are driven in the two-dimensional direction or three-dimensional direction.
In the conventional transfer feeder of the structure described above, a rear cushion cylinder composed of an air cylinder is utilized for pushing the cam follower of the feed lever to the feed cam, and an air pressure to be supplied to the rear cushion cylinder is set to the maximum value necessary in consideration of the condition that a weight of a movable member is generally subjected to the maximally accelerated speed at the maximum production speed (maximum operation speed) of the press.
For the reason described above, in the described conventional transfer feeder, a pushing force at the maximum production speed is applied to the feed cam through the cam follower even in a case where the production speed (operation speed) of the press does not reach the maximum production speed, resulting in an early reduction of the lifetime of the driving system of the transfer feeder and an increase of power consumption, thus being inconvenient.
Therefore, an object of the present invention is to provide a dynamic balancer circuit of a transfer feeder capable of controlling a pushing force of a rear cushion cylinder to an optimum value in response to a production speed of a press to thereby improve the lifetime of a driving system and to reduce the power consumption.